diff --git a/Parser/pegen/pegen.c b/Parser/pegen/pegen.c
index a51c8aa..c8f5c95 100644
--- a/Parser/pegen/pegen.c
+++ b/Parser/pegen/pegen.c
@@ -1161,7 +1161,7 @@
     if (!second_str) {
         return NULL;
     }
-    ssize_t len = strlen(first_str) + strlen(second_str) + 1;  // +1 for the dot
+    Py_ssize_t len = strlen(first_str) + strlen(second_str) + 1;  // +1 for the dot
 
     PyObject *str = PyBytes_FromStringAndSize(NULL, len);
     if (!str) {